the comet stream was closed without the final chunk

the comet stream was closed without the final chunk

Streaming responses declare Transfer-Encoding: chunked and the data goes out
framed by chunked_content(), but on close the zero length chunk that
terminates the response was never sent.

With apache it went unnoticed: the daemon owned the client socket and simply
closed it. nginx instead parses the response, and every stream that renews
itself (RD_ENDTIME_DELTA, 240 seconds) looked truncated to it: "upstream
prematurely closed connection while reading upstream", one error line per
connected player per cycle.

The final chunk is added in User::stream_close(), which is already the place
where the daemon writes its last bytes before closing, and only for the
transports that really are chunked: websockets are not, and keep sending
their own close frame.

Measured: with 150 players the renewal of the streams produced 150 errors;
after the fix, 30 players and 30 stream reopenings give zero errors.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014M1jiEq9cHdE5SE5j6vFuE